The present invention relates to a tooth for the bucket or scoop of an earth-moving machine; such teeth are mounted on the free edge, or front, of the bottom wall of a bucket or scoop of such a machine. This front edge of a bucket or a scoop of an earth-moving machine acts, in use of the scoop, as a blade and the teeth with which it is provided serve to protect the edge and to penetrate the soil.
A number of problems occur in designing teeth for earth-moving machines due to the stresses to which these teeth are subject in operation and to the operations they have to perform. Teeth of this sort, in fact, are subjected, in operation, to considerable mechanical stresses, and to wear. They must, above all, have a form which facilitates their penetration into the ground, and they must, moreover, retain this form as long as possible during their operational life despite the wear to which they are subjected. The dimensions and shape of these teeth must also be able, as far as possible, to withstand the considerable forces which occur during operation. In addition, the connection of the teeth to the front edge of the bottom wall of the bucket or scoop must be sufficiently robust and secure, and the shape of the teeth must ensure good protection of the front edge of the said bottom wall.
In known constructions, the teeth for earth-moving machines comprise a tool body having an appendage for attaching the tooth to the front edge of the scoop. The said appendage may be in the form of a shank, or in the form of a fork. In the case of teeth connected to the scoop by a shank the shank is housed during operation in a tooth-holder casing, fixed to the front edge of the scoop, and is secured to this casing by means of a key or like means. In the case of teeth connected to the scoop by a fork, for example, in British Pat. No. 1,275,206, the two prongs of the fork are so placed as to grip the front edge of the bucket and they are then affixed thereto by through-bolts or by welding.
Teeth having a shank for connection to the scoop have the disadvantage that during operation disengagement of the key can occur, with consequent loss of the tooth. Moreover the shape of such a tooth does not always offer the best protection for the front edge of the bottom wall of the scoop. Teeth having a fork for connection to the scoop, however, due to symmetrical form and the way that connection is effected to the bottom wall of the scoop, as well as being firmer than the shank type connection and hence better able to withstand high stresses, are also better able to protect both the upper and lower surfaces of the bottom wall of the scoop. Such teeth have the disadvantage, however, of requiring replacement of the whole tooth when the tool body is worn out. This involves a considerable waste of material. One solution to this problem, which was attempted to avoid this disadvantage, is shown in the German Pat. No. 1,255,595. This involves providing the tooth with a removable tip, so that only the tip has to be replaced, and not the whole tooth when worn. In this case, however, there is the disadvantage that the removable tip has less mechanical strength than the one-piece tooth and is thus more susceptible to breakage and consequent loss of the tip. This disadvantage is further aggravated by the fact that whenever the loss of the tip is not noticed in time, damage also results to the fixed portion of the tooth which serves as holder for the removable tip.